{"id":"2224d0cd-a166-5d87-a079-7bc466018d88","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:c-reg-extracellular-iron-peroxide-removal","predicate":"decreases-net","statement":"In RPMI/FCS exposed to 5 mM ascorbate, added 5 µM FAC iron accelerated oxygen consumption/ascorbate oxidation but reduced detectable peroxide accumulation, showing that faster oxidation need not yield a larger steady peroxide pool.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"negative","is_public":true,"mechanism_event_id":"2e64bb08-2c43-5300-9adc-75a0b884bbd9","mechanism_event_label":"Iron sped up vitamin C oxidation while also helping remove the peroxide produced.","subject":{"id":"80537c07-6aa7-5a3b-9148-f7033ce3c0fd","slug":"ferric-ammonium-citrate","display_name":"Ferric ammonium citrate","entity_type_key":"chemical_species"},"object":{"id":"18a4b880-f4f3-5991-9062-76adbf68e350","slug":"extracellular-peroxide-accumulation","display_name":"Extracellular hydrogen peroxide accumulation","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"2e64bb08-2c43-5300-9adc-75a0b884bbd9","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:c-reg-extracellular-iron-peroxide-removal-event","event_type":"biochemical_relationship","label":"Iron sped up vitamin C oxidation while also helping remove the peroxide produced.","description":"In RPMI/FCS exposed to 5 mM ascorbate, added 5 µM FAC iron accelerated oxygen consumption/ascorbate oxidation but reduced detectable peroxide accumulation, showing that faster oxidation need not yield a larger steady peroxide pool.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"da1a7137-08f2-5a36-8bb6-377fbd32e327","slug":"vitamin-c","display_name":"Vitamin C","entity_type_key":"chemical_species"},"role":"nutrient context","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"38d0c4d9-53d1-5239-bfe3-c1b5e9b79085","slug":"ascorbate","display_name":"L-Ascorbate","entity_type_key":"small_molecule"},"role":"reducing agent","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"da9d64bc-69d4-5d97-90a4-8f0ed03e0ac8","slug":"hydrogen-peroxide","display_name":"Hydrogen peroxide","entity_type_key":"small_molecule"},"role":"net product/removal substrate","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"899c7ab0-6f81-5b38-a6bd-fbb33d66ac8d","slug":"oxygen","display_name":"Molecular oxygen","entity_type_key":"small_molecule"},"role":"measured dissolved gas","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"17a4b1a5-451a-563f-8f20-2de8f4b0af8e","slug":"ascorbyl-radical","display_name":"Ascorbyl radical","entity_type_key":"chemical_species"},"role":"parallel EPR readout","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""},{"entity":{"id":"80537c07-6aa7-5a3b-9148-f7033ce3c0fd","slug":"ferric-ammonium-citrate","display_name":"Ferric ammonium citrate","entity_type_key":"chemical_species"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":5,"notes":""},{"entity":{"id":"18a4b880-f4f3-5991-9062-76adbf68e350","slug":"extracellular-peroxide-accumulation","display_name":"Extracellular hydrogen peroxide accumulation","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":6,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"true","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Figure 2a–b; Oximetry Methods","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Cell-free medium oximetry; peroxide inferred from catalase-triggered oxygen release","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"5 mM ascorbate ±5 µM FAC iron; oxygen trace and 600 U catalase addition after about 15 min.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"FAC supplementation changes iron speciation as well as concentration; matching plasma total iron does not reconstruct transferrin binding or tissue interstitial chemistry. No clinical efficacy conclusion. The endpoint measures net peroxide and does not separately determine every elementary redox rate.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin C research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-c","display_name":"Vitamin C","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Cell-free bovine-serum-containing medium","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Iron sped up vitamin C oxidation while also helping remove the peroxide produced.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[c-reg-mojic] Extracellular iron diminishes anticancer effects of vitamin C: an in vitro study. (2014). https://pubmed.ncbi.nlm.nih.gov/25092529/ DOI: 10.1038/srep05955","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"RPMI-1640 +10% FCS","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"2f2f56b1-13df-5a4a-bb18-91ac6de24a9a","evidence_kind":"source_excerpt","locator":"Lines 1299-1311","start_line":1299,"end_line":1311,"excerpt":"### c-reg-extracellular-iron-peroxide-removal\nIn RPMI/FCS exposed to 5 mM ascorbate, added 5 µM FAC iron accelerated oxygen consumption/ascorbate oxidation but reduced detectable peroxide accumulation, showing that faster oxidation need not yield a larger steady peroxide pool.\nCondition category: normal\nnutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Iron sped up vitamin C oxidation while also helping remove the peroxide produced.\norganism: Cell-free bovine-serum-containing medium\ntissue_or_cell_type: RPMI-1640 +10% FCS\nexperimental_model: Cell-free medium oximetry; peroxide inferred from catalase-triggered oxygen release\nlimitations: FAC supplementation changes iron speciation as well as concentration; matching plasma total iron does not reconstruct transferrin binding or tissue interstitial chemistry. No clinical efficacy conclusion. The endpoint measures net peroxide and does not separately determine every elementary redox rate.\nexposure: 5 mM ascorbate ±5 µM FAC iron; oxygen trace and 600 U catalase addition after about 15 min.\ncross_nutrient: true\nevidence_location: Figure 2a–b; Oximetry Methods\n[c-reg-mojic] Extracellular iron diminishes anticancer effects of vitamin C: an in vitro study. (2014). https://pubmed.ncbi.nlm.nih.gov/25092529/ DOI: 10.1038/srep05955","model_system":"Cell-free medium oximetry; peroxide inferred from catalase-triggered oxygen release","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [c-reg-mojic] Extracellular iron diminishes anticancer effects of vitamin C: an in vitro study. 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